Technical Abstract:
A stand of cotton, var. DPL 5415, was established at UC Desert Research & Extension Center 27 March 2000. Seven insecticide treatments and a non-treated control were replicated four times in a randomized complete design. Insecticide treatments were as follows: Assail 70 WP (acetamiprid) at 0.075 and 0.1 lb ai/acre, Actara 25 WP (thiamethoxam) at 0.05 and 0.06 lb ai/acre, Provado 1.6 F (imidacloprid) at 0.05 lb ai/acre, Danitol 2.4EC (fenpropathrin) + Orthene 97S (acephate) at 0.2 and 0.5 lb ai/acre, and Thiodan 3 EC (endosulfan) at 1.0 lb ai/acre. Silverleaf whitefly adults were sampled from ten plants at random in each plot via the leaf turn method using the fifth main stem leaf from the terminal. Silverleaf whitefly nymphs were counted on 1.65 cm2 leaf disks from 5th position, main-stem terminal leaves extracted from ten randomly selected plants in each plot. Whitefly adults and nymphs were sampled on 6, 13, 20 & 27 June, 4, 11, 18 & 25 July, 1, 8 & 15. Seed cotton was hand picked from 0.002 acre per plot and seed cotton yield data were recorded. Seed cotton samples were ginned at the USDA-ARS Western Cotton Research Laboratory in Phoenix, AZ and lint samples were sent to the USDA/ARS Cotton Quality Research Station in Clemson, SC for stickiness and sugar analysis. There were no differences among the treatments for silverleaf whitefly means on any of the sampling dates except 25 July when Thiodan 3 EC at 1.0 lb ai/acre, Assail 70 WP at 0.1 lb ai/acre and Danitol 2.4 EC + Orthene 97S had adult means lower than the non-treated control, P# 0.05. There were no differences among the treatments for silverleaf whitefly seasonal means. Assail 70 WP at 0.1 lb ai/acre gave the best control of silverleaf whitefly nymphs through the season followed by Assail 70 WP at 0.075 and Danitol 2.4 EC + Orthene 97S and all three of these treatments had silverleaf whitefly seasonal means lower than the non-treated control. The seasonal means of silverleaf whitefly nymphs for both rates of Actara 25 WP, for Provado 1.6 F and for Thiodan 3 EC were not different from the non-treated control.